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Biomedical subjects

V ter Meulen

Publications and source records attributed to V ter Meulen.

At least 19 recordsLinked to original sources
PubMed2004

Monoamine oxidase inhibition and CNS immunodeficiency infection.

HIV invades CNS subcortical areas, particularly the dopamine-rich basal ganglia and induces a subcortical dementia. Data suggest that the basal ganglia dysfunction plays a critical role in the neuropsychiatric manifestation of HIV infection. Therefore, therapeutic approaches for HIV dementia nowadays wish to include apart from the highly active antiretroviral therapy (HAART) also adjunctive medication. In this short article, we report briefly on neurotoxicity associated with the immunodeficiency virus and discuss the effects of selegiline, a monoamine oxidase inhibitor which enhances dopamine availability in CNS on immunodeficiency virus-induced neurological disease.

Animals↗
PubMed2004

Dopamine deficits and regulation of the cAMP second messenger system in brains of simian immunodeficiency virus-infected rhesus monkeys.

The basal ganglia, structures rich in the neurotransmitter dopamine, are primarily affected during human immunodeficiency virus (HIV) infection. The authors measured levels of dopamine and its metabolites, homovanillic acid and 3,4-dihydroxyphenylacetic acid, in brains of uninfected and simian immunodeficiency virus (SIV)-infected rhesus monkeys during the asymptomatic stage of the infection. Moreover, the authors investigated changes in cyclic adenosine monophosphate (cAMP) and cAMP response element-binding protein (CREB), two factors involved in the signaling pathway of dopamine. The brain regions examined were the nucleus accumbens and the corpus amygdaloideum, which are limbic structures of the basal ganglia that are involved in the pathophysiology of psychiatric disorders and substance abuse. Dopamine content was reduced in both regions of SIV-infected monkeys compared to uninfected animals. Moreover, dopamine deficits were associated with a decrease in expression of total CREB. Intracellular concentrations of cAMP were decreased in nucleus accumbens and remained unchanged in corpus amygdaloideum of SIV-infected macaques. Changes in dopamine signaling were not related to pathology or viral load of the investigated animals. The results suggest that dopamine defects precede neurologic deficits and implicate dysfunction of the dopaminergic system in the etiopathogenesis of HIV dementia. Therefore, affective complications in HIV subjects should not be interpreted only as reactive psychological changes. The alterations in the mesolimbic dopaminergic system during asymptomatic stage of SIV infection implicate a biological background for psychiatric disorders in HIV infection.

3,4-Dihydroxyphenylacetic Acid↗
PubMed2003

Dendritic cells and measles virus infection.

Measles is a major cause of childhood mortality in developing countries which is mainly attributed to the ability of measles virus (MV) to suppress general immune responses. Paradoxically, virus-specific immunity is efficiently induced, which leads to viral clearance from the host and confers long-lasting protection against reinfection. As sensitisers of pathogen encounter and instructors of the adaptive immune response, dendritic cells (DCs) may play a decisive role in the induction and quality of the MV-specific immune activation. The ability of MV wild-type strains in particular to infect DCs in vitro is dearly established, and the receptor binding haemagglutinin protein of these viruses essentially determines this particular tropism. DC maturation as induced early after MV infection is likely to be of crucial importance for the induction of MV-specific immunity. DCs may, however, be instrumental in MV-induced immunosuppression. (1) T cell depletion could be brought about by DC-T cell fusion or TRAIL-mediated induction of apoptosis. (2) Inhibition of stimulated IL-12 production from MV-infected DCs might affect T cell responses in qualitative terms in favouring Th2 and suppressing Th1 responses. (3) The viral glycoprotein complex expressed at high levels on infected DCs late in infection is able to directly inhibit T cell proliferation by surface contact-dependent negative signalling. This most likely accounts for the failure of infected DC cultures to stimulate allogeneic and inhibit mitogen-stimulated T cell proliferation in vitro and the pronounced proliferative unresponsiveness of T cell ex vivo to polyclonal and antigen-specific stimulation which is a central finding of MV-induced immunosuppression.

Dendritic Cells↗
PubMed2002

Involvement of dopamine in the progression of AIDS Dementia Complex.

HIV compromises immunological functions. Immune responses are regulated to a great extent by several molecules such as cytokines, neurotransmitters and hormones which interact with different immune effector cells and ultimately mediate the homeostatic responses to disease. Among these mediators, dopamine plays an important role. In this article we review AIDS Dementia Complex (ADC) and describe lines of evidence implying increased dopamine availability as a potent mediator of neurologic deficits in HIV infection and a factor exhibiting adverse effects on the progression of ADC.

AIDS Dementia Complex↗
PubMed2002

Macaque animal model for HIV-induced neurological disease.

The pathogenesis of HIV-induced neurological disorders is still incompletely understood. Since many aspects of this disease are difficult to explore in humans, animal models are necessary to fill the gaps in our knowledge. Based on the high concordance with the human system, the SIV-infection of macaques currently provides the best animal model to study pathogenesis, therapy and prevention of HIV-infection. In this review, important features of the CNS-infection in this model are outlined. Recent virological, immunological, neurophysiological and neurochemical findings obtained with this animal model are presented and key factors in the development of neurological disease are identified.

AIDS Dementia Complex↗
PubMed2002

Parkinsonism in HIV dementia.

A great number of human immunodeficiency virus (HIV)-infected patients develop a central nervous system disorder, commonly called HIV dementia or AIDS dementia complex (ADC). HIV dementia is independent of opportunistic infections and is due to the virus itself. Symptoms include psychomotor slowing, apathy and motor disorders similar to the bradykinesia and postural and gait abnormalities observed in late Parkinson's disease. Consequently, HIV has been discussed during the last few years as an additional cause for parkinsonism, and parkinsonian syndromes as manifestations of HIV dementia. Moreover, the early phase of HIV infection gains increasing interest because of studies which report subtle neurological symptoms at this stage. Accordingly, we found in SIV-infected monkeys that dopamine is reduced by 44% within as few as two months of infection, indicating that changes during early infection must be thoroughly evaluated. In this short review, we discuss alterations in the nigrostriatal dopaminergic system during early and late immunodeficiency virus infection and the common clinical and biochemical features shared by HIV dementia and Parkinson's disease.

AIDS Dementia Complex↗
PubMed2002

Psychiatric complications in human immunodeficiency virus infection.

Human immunodeficiency virus (HIV) infection is associated with psychiatric complications, including cognitive impairment, affective disorders, and psychosis. These psychiatric complications impair quality of life, affect disease prognosis, and impede treatment by compromising medication adherence. They also increase the likelihood of HIV transmission, either directly or via their high prevalence rate among drug abusers. In this article, the authors provide a brief overview of the most common psychiatric complications associated with HIV infection and discuss the role of dopamine as a link between psychiatric manifestations and the progression of immunodeficiency infection.

AIDS Dementia Complex↗
PubMed2001

Influenza vaccination in MS: absence of T-cell response against white matter proteins.

BACKGROUND: Natural infections bear the risk of triggering MS bouts, whereas epidemiologic studies have not delineated an increased risk for disease activity after influenza virus vaccination. OBJECTIVE: To examine influenza A virus-specific and myelin protein-reactive T-cell frequencies by interferon gamma (IFNgamma)-enzyme-linked immunospot and the response of these cells by IFNgamma-reverse transcription (RT) PCR after immunization and any incidental upper respiratory tract infection (URI) in 12 patients with MS (seven with a relapsing-remitting course; five with a secondary progressive course; Kurtzke Expanded Disability Status Scale [EDSS] score from 1.0 to 6.5, without immunosuppressive treatment) and 28 healthy volunteers. RESULTS: A cellular immune response against influenza A virus was mounted in both populations at 2 weeks after vaccination. Patients with MS showed a higher relative increase (p = 0.008) than controls with respect to the number of influenza-specific T cells. Mean antibody responses against influenza A virus were increased in both populations after 2 weeks (p < 0.01). Despite these virus-specific reactions, no increase in T-cell frequencies responsive to human myelin basic protein (MBP) or recombinant human myelin oligodendrocyte protein (MOG) was observed after immunization, arguing against a general immune stimulation by influenza vaccination. In contrast, MBP-specific T-cell responses became detectable in several individuals after febrile infection. CONCLUSION: These data support the clinical observations that influenza vaccination is effective and safe in patients with MS with respect to cellular immunoreactivity against two main CNS myelin proteins.

Adult↗
PubMed2001

Enhancement of central nervous system pathology in early simian immunodeficiency virus infection by dopaminergic drugs.

Human immunodeficiency virus infection (HIV) at late stages of the disease is accompanied by neurological complications, including motor, behavioral and cognitive impairment. Using simian immunodeficiency virus (SIV)-infected rhesus monkeys, an animal model of HIV infection, we found that during the asymptomatic SIV infection dopamine (DA) deficits are early components of central nervous system (CNS) dysfunction. To investigate the role of the DA system in SIV infection and to restore the DA deficiency, we administered selegiline, an agent with DAergic and neuroprotective properties, to SIV-infected monkeys. Selegiline increased DA availability but induced CNS vacuolization, SIV encephalitic lesions, and enhanced CNS viral replication during early SIV infection. The pathological changes seem to be mediated by DA, as treatment with L-DOPA, the precursor of DA, had similar effects. We propose that any natural or induced DAergic dysregulation which results in increased DA availability may potentiate HIV-associated neurological disease (ND). Our findings raise new questions regarding the pathogenesis of HIV-ND and generate concerns about the safety of dopaminergic drugs in the clinical management of HIV-infected patients.

AIDS Dementia Complex↗
PubMed2001

Neurotransmission in HIV associated dementia: a short review.

Human immunodeficiency virus (HIV) infection is frequently associated with specific neurological and psychiatric symptoms. Our understanding of how HIV-related CNS deficits develop is still preliminary and the cause remains obscure. However, some clues have emerged which may clarify uncertainties. Following a brief discussion of the epidemiology underlying neuropathological mechanisms and clinical symptoms in HIV-infected patients, we focus our attention on neurochemical data obtained by studies in humans and rhesus monkeys which provide information on the effect of the retroviral infection on neurotransmission and assist in the evaluation of potential therapeutic treatments.

AIDS Dementia Complex↗
PubMed2001

Disruption of Akt kinase activation is important for immunosuppression induced by measles virus.

Surface-contact-mediated signaling induced by the measles virus (MV) fusion and hemagglutinin glycoproteins is necessary and sufficient to induce T-cell unresponsiveness in vitro and in vivo. To define the intracellular pathways involved, we analyzed interleukin (IL)-2R signaling in primary human T cells and in Kit-225 cells. Unlike IL-2-dependent activation of JAK/STAT pathways, activation of Akt kinase was impaired after MV contact both in vitro and in vivo. MV interference with Akt activation was important for immunosuppression, as expression of a catalytically active Akt prevented negative signaling by the MV glycoproteins. Thus, we show here that MV exploits a novel strategy to interfere with T-cell activation during immunosuppression.

Androstadienes↗
PubMed2001

Measles virus interactions with cellular receptors: consequences for viral pathogenesis.

Although CNS complications occurring early and late after acute measles are a serious problem and often fatal, the transient immunosuppression lasting for several weeks after the rash is the major cause of measles-related morbidity and mortality worldwide. This review is focused on the interactions of measles virus (MV) with cellular receptors on neural and lymphoid cells which are important elements in viral pathogenesis. First, the cognate MV receptors, CD46 and CD150, are important components of viral tropism by mediating binding and entry. Second, however, additional unknown cellular surface molecules may (independently of viral uptake) after interaction with the MV glycoprotein complex act as signaling molecules and thereby modulate cellular survival, proliferation, and specific functions.

Antigens, CD↗
PubMed2001

CD150 (SLAM) is a receptor for measles virus but is not involved in viral contact-mediated proliferation inhibition.

Measles virus (MV) interacts with cellular receptors on the surface of peripheral blood lymphocytes (PBL) which mediate virus binding and uptake. Simultaneously, the direct contact of the viral glycoproteins with the cell surface induces a negative signal blocking progression to the S phase of the cell cycle, resulting in a pronounced proliferation inhibition. We selected a monoclonal antibody (MAb 5C6) directed to the surface of highly MV-susceptible B cells (B95a), which inhibits binding to and infection of cells with MV wild-type and vaccine strains. By screening a retroviral cDNA library from human splenocytes (ViraPort; Stratagene) with this antibody, we cloned and identified the recognized molecule as signaling lymphocytic activation molecule (SLAM; CD150), which is identical to the MV receptor recently found by H. Tatsuo et al. (Nature 406:893-897, 2000). After infection of cells, and after surface contact with MV envelope proteins, SLAM is downregulated from the cell surface of activated PBL and cell lines. Although anti-SLAM and/or anti-CD46 antibodies block virus binding, they do not interfere with the contact-mediated proliferation inhibition. In addition, the cell-type-specific expression of SLAM does not correlate with the sensitivity of cells for proliferation inhibition. The data indicate that proliferation inhibition induced by MV contact is independent of the presence or absence of the virus-binding receptors SLAM and CD46.

Animals↗
PubMed2001

Recombinant measles viruses expressing altered hemagglutinin (H) genes: functional separation of mutations determining H antibody escape from neurovirulence.

Measles virus (MV) strain CAM/RB, which was adapted to growth in the brain of newborn rodents, is highly neurovirulent. It has been reported earlier that experimentally selected virus variants escaping from the monoclonal antibodies (MAbs) Nc32 and L77 to hemagglutinin (H) preserved their neurovirulence, whereas mutants escaping MAbs K71 and K29 were found to be strongly attenuated (U. G. Liebert et al., J. Virol. 68:1486-1493, 1994). To investigate the molecular basis of these findings, we have generated a panel of recombinant MVs expressing the H protein from CAM/RB and introduced the amino acid substitutions thought to be responsible for antibody escape and/or neurovirulence. Using these recombinant viruses, we identified the amino acid changes conferring escape from the MAbs L77 (377R-->Q and 378M-->K), Nc32 (388G-->S), K71 (492E-->K and 550S-->P), and K29 (535E-->G). When the corresponding recombinant viruses were tested in brains of newborn rodents, we found that the mutations mediating antibody escape did not confer differential neurovirulence. In contrast, however, replacement of two different amino acids, at positions 195G-->R and 200S-->N, which had been described for the escape mutant set, caused the change in neurovirulence. Thus, antibody escape and neurovirulence appear not to be associated with the same structural alterations of the MV H protein.

Animals↗
PubMed2001

Inhibition of major histocompatibility complex class II-dependent antigen presentation by neutralization of gamma interferon leads to breakdown of resistance against measles virus-induced encephalitis.

BALB/c mice are resistant to measles virus (MV)-induced encephalitis due to their strong MV-specific CD4(+) T-cell response. Resistance is broken by neutralization of gamma interferon with monoclonal antibodies, indicating an important role for this pleiotropic cytokine. Here, we demonstrate that mouse gamma interferon has no direct antiviral effect in vitro and in vivo. The breakdown of resistance is due neither to a switch in the T-helper response nor to an impaired migration of CD4(+) T cells. Neutralization of gamma interferon interferes with the major histocompatibility complex class II-dependent antigen presentation and subsequent proliferation of CD4(+) T cells in vitro and in vivo. In consequence, the reduction in numbers of CD4(+) T cells below a protective threshold leads to susceptibility to MV-induced encephalitis.

Animals↗
PubMed2001

Measles virus induced immunosuppression: targets and effector mechanisms.

A profound, transient suppression of immune functions during and after the acute infection is the major cause of more than one million cases of infant deaths associated with measles worldwide. Concommittant with the generation of an efficient measles virus (MV) specific immunity, immune responses towards other pathogens are strongly impaired and provide the basis for the establishment and severe course of opportunistic infections. The molecular basis for MV-induced immunosuppression has not been resolved as yet. Similar to other immunosuppressive viruses, MV is lymphotropic and viral nucleic acid and proteins are detectable in peripheral blood mononuclear cells (PBMC). It is considered central to MV-induced immunosuppression that PBMC isolated from patients largely fail to proliferate in response to antigen specific and polyclonal stimulation. The low abundancy of MV-infected PBMC suggests that MV-induced immunosuppression is not directly caused by infection-mediated cell loss or fusion, but rather by indirect mechanisms such as deregulation of cytokines or surface contact-mediated signaling which may lead to apoptosis or impair the proliferative response of uninfected PBMC. Evidence for a role of any of these mechanisms was obtained in vitro, however, much has still to be learned about the tropism of MV and its interactions with particular host cells such as dendritic cells in vivo.

Animals↗
PubMed2000

Brain choline acetyltransferase reduction in SIV infection. An index of early dementia?

HIV infection at late stages is associated with neurological complications including impaired motor and cognitive functions. We used simian immunodeficiency (SIV)-infected rhesus monkeys, an animal model of HIV infection, to investigate changes in choline acetyltransferase (ChAT) activity, a biochemical marker of cognitive function, in post-mortem brains during early, asymptomatic SIV infection and AIDS. ChAT activity was dramatically reduced in putamen and hippocampus already during asymptomatic infection. In animals with AIDS, ChAT activity was further decreased. The reduction of ChAT was not related to brain viral load or CNS pathological lesions. Our results demonstrate deficits in ChAT activity already during the first months of SIV infection and imply that cognitive dysfunction may occur early in immunodeficiency viral infections.

AIDS Dementia Complex↗